Unsaturated polyesters prepared from a dicarboxylic acid and dibromoneopentyl glycol

ABSTRACT

Unsaturated esters can be prepared from dicarboxylic acids and dibromoneopentyl glycol with improved resin color in a shorter reaction time with minimal corrosion of metallic reaction vessels and with a net energy saving by the process using an aryl sulfonic acid as the esterification catalyst and following completion of the reaction neutralizing the acid catalyst.

CROSS-REFERENCE TO COPENDING APPLICATION

This application is a divisional of our copending application U.S. Ser.No. 189,236, filed Sept. 22, 1980 and now U.S. Pat. No. 4,384,109 whichis a continuation-in-part of our copending application, U.S. Ser. No.099,259, filed Dec. 3, 1979 now abandoned.

BACKGROUND OF THE INVENTION

Unsaturated polyester resins are conventionally prepared by reactingdibasic acids; i.e., phthalic anhydride, maleic anhydride, etc., anddifunctional alcohols; i.e., ethylene glycol, propylene glycol, etc., instainless steel reactors at temperatures between 170°-200° C. Corrosionof stainless steel is slow enough in these systems that it does not havean adverse effect on either reactor life or resin color.

Synthesis of unsaturated polyester resins such as those described inU.S. Pat. No. 3,507,933, i.e., fire retardant resins prepared fromphthalic anhydride, maleic anhydride, and dibromoneopentyl glycol,results in corrosion problems when carried out in stainless steelreactors, and this in turn leads to color problems.

The use of sulfuric acid and sulfonic acids as catalysts forpolyesterification reactions using saturated dibasic acids are known inthe prior art, e.g., P. J. Flory disclosed the use of p-toluene sulfonicacid (p-TSA) as a catalyst for the reaction of adipic acid and ethyleneglycol in 1939. Later attempts to use strong acid catalysts in thepreparation of unsaturated polyester resins have been less thansuccessful. Weakly acidic or basic catalysts are usually required forreactions involving aliphatic diols in order to prevent dehydration toether or olefin. It has also been pointed out that acid catalysts suchas sulfuric acid or p-TSA, while increasing the rate of bothesterification and isomerization, usually cause color formation andother detrimental side reactions.

Some of these adverse reactions caused by the presence of sulfuric, orsulfonic acids, include premature gelation of the styrenated andunstyrenated resins and the loss of glycol from the cook due to theformation of volatile ethers. It has been shown that as little as 50 ppmof sulfuric acid will catalyze the formation of ethers from aliphaticdiols at polyester reaction temperatures.

SUMMARY OF THE INVENTION

Unsaturated polyesters containing dibromoneopentyl glycol for at least apart of the polyol are prepared with less color, in shorter reactiontimes and at lower temperatures by the process wherein an aryl sulfonicacid is used as the catalyst and that catalyst is neutralized followingesterification by the addition of an acid scavenger to the reactionmixture.

DETAILS OF THE INVENTION

An unsaturated polyester is a condensation polymer produced bycondensing approximately equimolar proportions of at least onedicarboxylic acid, at least a portion of which contains ethylenicunsaturation, with at least one polyol, which for purposes of thisinvention, must be made up at least in part of dibromoneopentyl glycol.Examples of such unsaturated acids include maleic, fumaric, itaconic andothers. The remainder, if any, of the dicarboxylic acids are usuallyeither saturated normal aliphatics, such as adipic acid, succinic acid,tetrahydrophthalic acid and the like or aromatic diacids, such asphthalic acid, isophthalic acid or the like. The term dicarboxylic acid,as used herein, is intended to embrace the anhydride as well.

The unsaturated acid provides the unsaturation needed for curing theresin. Therefore, the actual ratio of unsaturated acid to saturated acidwill be dictated by the degree of crosslinking desired in the curedproduct. That degree of crosslinking may be predetermined by simplepreliminary experiments as is standard in the polyester art.

The polyol to be used is dibromoneopentyl glycol. Other nonhalogenatedglycols may be used in small amounts without affecting the inventiveconcept. However, when using aryl sulfonic acids as the esterificationcatalysts, those nonhalogenated glycols form ethers and otherundesirable by-products. The present invention appears to be singularlywell adapted for use with dibromoneopentyl glycol which must form thesubstantial majority of the polyol.

The acid scavenger to be used in the process is any compound that willneutralize the acid catalyst through formation of a salt, ester, aminesalt or by other means. Typical of such scavengers are the oxiranecompounds, such as epichlorohydrin, the diglycidyl ether of a polyol as,for example, the diglycidyl ether of an aliphatic glycol soldcommercially as DER-736 and other epoxy compounds; oxetane compoundssuch as bis-2,2-(dibromomethyl)oxetane; amines such as diethanolamine ortriethanolamine; soluble salts of weak acids such as sodium acetate.

The esterification catalyst is an aryl sulfonic acid or an ester of suchan acid. Typical of those acids are benzene sulfonic acid and p-toluenesulfonic acid. The amount of catalyst can vary between about 0.05 and 3percent by weight of the reactants. Preferably, the amount is between0.1 and 0.4 weight percent.

The polyester is made in generally conventional manner except asotherwise described herein. In one embodiment, the acid,dibromoneopentyl glycol and catalyst are introduced into a suitableesterification reaction vessel equipped with means for removing water ofesterification suitably as it is formed in the reaction. The reactantsare blanketed with an inert atmosphere, preferably nitrogen gas, thenagitated and heated to effect the reaction for a desired period of time.The reaction temperature can range from about 100° to 200° C.,preferably from 135° to 165° C. The exact reaction time will depend onthe resin formulation, the amount of catalyst, the reaction temperatureand pressure and the inert gas sparge rate.

The degree of reaction is conveniently determined by measuring the acidnumber or by measuring the amount of water liberated in the reaction.The reaction is discontinued when the product has a desired acid number,e.g., an acid number of 40 or below. After the reaction has been carriedto the desired degree of completion, the acid scavenger is added.

In another embodiment, the dibromoneopentyl glycol is melted and thearyl sulfonic acid catalyst dissolved therein. While still molten, theacid scavenger may be added to neutralize the mixture by converting theacid to the corresponding ester. Such dissolved or dispersed esters areuseful in causing esterification of the glycol and acid or anhydride.During the cook, the catalyst acid scavenger ester splits to form theacid which acts as a catalyst. Prior to styrenation of the resin solids,the resin is treated with a scavenger to remove strong noncarboxylicacids. The solid solution resulting from dissolving the aryl sulfonicacid catalyst in the melted dibrononeopentyl comprises a catalyticamount up to 1 weight percent of an aryl sulfonic acid indibromoneopentyl glycol.

Alternatively, the aryl sulfonic acid and glycol can be mixed to form aphysical blend which is useful as a premix for preparingglycol-carboxylic acid esters.

The resin is then recovered and blended with an ethylenicallyunsaturated monomer of copolymerizable with the unsaturated polyesterpolymers to form a blend wherein the weight ratio of polyester tomonomer is in the range from about 4:1 to about 1:2. Such ethylenicallyunsaturated monomers are well known and include styrene, chlorostyrene,vinyl toluene, divinylbenzene, dicyclopentadiene alkenoate, acrylic andmethacrylic acid, diallyl phthalate and like unsaturated monomers ormixtures thereof.

These polyester blends with unsaturated monomers should contain about 20to about 60 percent by weight and preferably 30-50 percent by weight ofthe monomers based on the weight of the polyester. A small amount of aninhibitor such as tertiary butyl catechol, hydroquinone, or the like,may be added to this mixture.

The final blend is a crosslinkable polyester composition which is usefulto make laminates, castings or coatings.

Laminates can be made by mixing into the crosslinkable composition, freeradical forming catalysts in known amounts and adding this mixture to asuitable fibrous reinforcement such as carbon fibers, fibrous glass orinorganic fibers.

Examples of these catalysts are benzoyl peroxide, tertiary butylperoxide, methylethyl ketone peroxide and the like. It is frequently ofvalue to add accelerators such as cobalt naphthenate, dimethyl anilineand the like.

The polyester resin is rolled, sprayed or impregnated into the fibrousreinforcement such as fibrous glass or is used in filled compositionsand cured in a manner well known in the art. When fibrous glass is used,it can be in any form such as chopped strands, filaments, glass ribbons,glass yarns or reinforcing mats. Typical fillers include calciumcarbonate and aluminum trihydrate.

The following examples are presented to illustrate but not limit theinvention.

EXAMPLE 1

The laboratory cooks were carried out in a 2 liter resin flask, equippedwith a mechanical stirrer, a stainless steel N₂ sparge tube, a stainlesssteel thermowell, and a steam heated (100° C.) partial condenserfollowed by a Dean-Stark tube followed by a water cooled condenser. Thereaction heat source was two 275 watt infrared lamps and the whole resinflask was kept in a hot air oven.

The resin flask was charged with 800 grams (3.05 moles) of commercialdibromoneopentyl glycol, 170 grams (1.73 moles) of maleic anhydride, 110grams (0.74 mole) of phthalic anhydride and 80 grams (4.44 moles) ofwater.

The reactor was sparged with N₂ (1190 cc/min) to remove air from thesystem prior to the start of the reaction and to aid in the removal ofwater after the reaction was started. [For comparative purposes, thecook time is considered to be that part of the cycle from the time thereaction temperature reached 125° C. until the reaction was terminated.]

The temperature controller was set at 135° C. and the reaction started.The reaction reached 125° C. in about 45 minutes and 135° C. in 55minutes. The reaction temperature was maintained at 135° C. until theacid number reached 29. (The usual acid number for making polyesters is30±2.) The cook time was 22 hours.

The crude alkyd was poured into a polytetrafluoroethylene coated pan andallowed to cool.

Samples were made up for testing by dissolving 75 grams of alkyd in 25grams of styrene, containing 0.02 gram of toluhydroquinone. Thestyrenated resin had the following properties:

    ______________________________________                                        Gardner Color          8.7                                                    SPI Gel Time           5.1 min.                                               SPI Peak Time          6.9 min.                                               SPI Peak Exotherm      188° C.                                         ______________________________________                                    

To a sample of this styrenated resin was added 1 weight percentepichlorohydrin to bleach the color caused by dissolved iron bromide.The bleached sample had the following properties:

    ______________________________________                                        Gardner Color          3.9                                                    SPI Gel Time           6.1 min.                                               SPI Peak Time          8.1 min.                                               SPI Peak Exotherm      213° C.                                         ______________________________________                                    

EXAMPLE 2

The above procedure was repeated except that 2.1 grams (0.011 mole) ofp-TSA was added to the reactor along with the charge. The reactionrequired 5.0 hours to reach an acid number of 30. Samples of styrenatedresin were made up as in Example 1 and the following results wereobtained:

    ______________________________________                                                   Without     With                                                              Epichlorohydrin                                                                           Epichlorohydrin                                        ______________________________________                                        Gardner Color                                                                              2.4           2.4                                                SPI Gel Time 1.6 min.      6.6 min.                                           SPI Cure Time                                                                              2.7 min.      8.8 min.                                           SPI Peak Exotherm                                                                          133° C.                                                                              209° C.                                     ______________________________________                                    

EXAMPLE 3

p-Toluene sulfonic acid (TSA), 3.6 grams, was added to 1200 grams ofmolten (110° C.) dibromoneopentyl glycol prepared as described in U.S.Pat. No. 3,932,541 prior to neutralization with an oxirane. To themolten solution was added 23 grams of a commercial polyglycol diepoxidehaving an epoxide equivalent weight of 175-205 and sold commercially asD.E.R.® 736, to neutralize the solution and to convert any residualhydrogen bromide or TSA to their corresponding esters. The moltenmixture was then allowed to solidify and crushed.

The DBNPG-TSA mixture was converted to an unsaturated polyester resinaccording to the procedure of Example 1, except as noted below.

A mixture of maleic (192 grams, 1.96 moles) and phthalic anhydride (295grams, 1.99 moles) were premelted and heated to 140° C. The solidDBNPG-TSA (1048 grams, 4.0 moles) was added to the molten anhydrides asrapidly as possible. During the addition, the reactor temperature fellto ˜75° C. The mixture was then heated rapidly to 160° C. and maintainedthere until the acid number reached approximately 37. The reaction time,as measured from the time the reaction temperature reached 160° C., was7 hours.

The crude alkyd was poured into a pan coated with Teflon® and allowed tocool.

Samples were made up for testing by dissolving 75 grams of alkyd in 25grams of styrene, containing 0.02 gram of toluhydroquinone. Thestyrenated resin (25 percent styrene) had the following properties:

    ______________________________________                                                     Without                                                                       Epi-      With Epi-                                                           chlorohydrin                                                                            chlorohydrin (1%)                                      ______________________________________                                        Gardner Color  >4          4                                                  Gardner Viscosity                                                                            >Z-6        Z-51/2                                             SPI Gel Time (min)                                                                           2.2         4.1                                                SPI Cure Time (min)                                                                          3.3         5.6                                                SPI Peak Exotherm (°C.)                                                               176         213                                                ______________________________________                                    

EXAMPLE 4

In a similar experiment, a mechanical mixture of 1048 grams (4.0 moles)of DBNPG and 3.15 grams of TSA was added to a molten mixture of 192grams (1.96 moles) of maleic anhydride and 295 grams (1.99 moles) ofphthalic anhydride.

Reaction time, measured from 160° C., was 7 hours and the alkyd had anacid number of 34.2.

Samples of the resin prepared as in Example 2 had the followingproperties:

    ______________________________________                                                     Without                                                                       Epi-      With Epi-                                                           chlorohydrin                                                                            chlorohydrin (1%)                                      ______________________________________                                        Gardner Color  4.5         4                                                  Gardner Viscosity                                                                            Z-51/2      Z-41/2                                             SPI Gel Time (min)                                                                           3.4         5.1                                                SPI Cure Time (min)                                                                          4.7         6.9                                                SPI Peak Exotherm (°C.)                                                               182         211                                                ______________________________________                                    

What is claimed is:
 1. A composition useful for making polyesters whenreacted with a polycarboxylic acid, said composition comprising a solidsolution of catalytic amounts of up to about 1 weight percent of an arylsulfonic acid in dibromoneopentyl glycol.
 2. The composition of claim 1wherein the aryl sulfonic acid and any residual hydrogen bromide isneutralized with an acid scavenger.
 3. The composition of claim 2wherein said acid scavenger is an oxirane compound.
 4. The compositionof claim 3 wherein said oxirane compound is a glycidyl ether.
 5. Thecomposition of claim 3 wherein said oxirane compound is epichlorohydrin.6. The composition of claim 1 wherein said aryl sulfonic acid isparatoluene-sulfonic acid.